Water

22 pages, 12273 KiB

Open AccessEditor’s ChoiceArticle

Experimental and Numerical Analysis of a Dam-Break Flow through Different Contraction Geometries of the Channel

by Selahattin Kocaman, Hasan Güzel, Stefania Evangelista, Hatice Ozmen-Cagatay and Giacomo Viccione

Water 2020, 12(4), 1124; https://doi.org/10.3390/w12041124 - 15 Apr 2020

Cited by 44 | Viewed by 6897

Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding [...] Read more.

Dam-break wave propagation usually occurs over irregular topography, due for example to natural contraction-expansion of the river bed and to the presence of natural or artificial obstacles. Due to limited available dam-break real-case data, laboratory and numerical modeling studies are significant for understanding this type of complex flow problems. To contribute to the related field, a dam-break flow over a channel with a contracting reach was investigated experimentally and numerically. Laboratory tests were carried out in a smooth rectangular channel with a horizontal dry bed for three different lateral contraction geometries. A non-intrusive digital imaging technique was utilized to analyze the dam-break wave propagation. Free surface profiles and time variation of water levels in selected sections were obtained directly from three synchronized CCD video camera records through a virtual wave probe. The experimental results were compared against the numerical solution of VOF (Volume of Fluid)-based Shallow Water Equations (SWEs) and Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε turbulence model. Good agreements were obtained between computed and measured results. However, the RANS solution shows a better correspondence with the experimental results compared with the SWEs one. The presented new experimental data can be used to validate numerical models for the simulation of dam-break flows over irregular topography. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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22 pages, 4830 KiB

Open AccessEditor’s ChoiceArticle

Use of Heavy Metal Content and Modified Water Quality Index to Assess Groundwater Quality in a Semiarid Area

by Ehsan Kamali Maskooni, Mehran Naseri-Rad, Ronny Berndtsson and Kei Nakagawa

Water 2020, 12(4), 1115; https://doi.org/10.3390/w12041115 - 14 Apr 2020

Cited by 70 | Viewed by 7438

Abstract

Groundwater is a major source of drinking and agricultural water supply in arid and semiarid regions. Poor groundwater quality can be a threat to human health especially when it is combined with hazardous pollutants like heavy metals. In this study, an innovative method [...] Read more.

Groundwater is a major source of drinking and agricultural water supply in arid and semiarid regions. Poor groundwater quality can be a threat to human health especially when it is combined with hazardous pollutants like heavy metals. In this study, an innovative method involving entropy weighted groundwater quality index for both physicochemical and heavy metal content was used for a semiarid region. The entropy weighted index was used to assess the groundwater’s suitability for drinking and irrigation purposes. Thus, groundwater from 19 sampling sites was used for analyses of physicochemical properties (electrical conductivity—EC, pH, K⁺, Ca²⁺, Na⁺, SO₄²⁻, Cl⁻, HCO₃⁻, TDS, NO₃⁻, F⁻, biochemical oxygen demand—BOD, dissolved oxygen—DO, and chemical oxygen demand—COD) and heavy metal content (As, Ca, Sb, Se, Zn, Cu, Ba, Mn, and Cr). To evaluate the overall pollution status in the region, heavy metal indices such as the modified heavy metal pollution index (m-HPI), heavy metal evaluation index (HEI), Nemerow index (NeI), and ecological risks of heavy metals (ERI) were calculated and compared. The results showed that Cd concentration plays a significant role in negatively affecting the groundwater quality. Thus, three wells were classified as poor water quality and not acceptable for drinking water supply. The maximum concentration of heavy metals such as Cd, Se, and Sb was higher than permissible limits by the World Health Organization (WHO) standards. However, all wells except one were suitable for agricultural purposes. The advantage of the innovative entropy weighted groundwater quality index for both physicochemical and heavy metal content, is that it permits objectivity when selecting the weights and reduces the error that may be caused by subjectivity. Thus, the new index can be used by groundwater managers and policymakers to better decide the water’s suitability for consumption. Full article

(This article belongs to the Section Water Quality and Contamination)

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16 pages, 4665 KiB

Open AccessEditor’s ChoiceArticle

Numerical Investigation of a High-Speed Electrical Submersible Pump with Different End Clearances

by Ling Zhou, Wanhong Wang, Jianwei Hang, Weidong Shi, Hao Yan and Yong Zhu

Water 2020, 12(4), 1116; https://doi.org/10.3390/w12041116 - 14 Apr 2020

Cited by 42 | Viewed by 4401

Abstract

The end clearance of the impeller is one of the most important structural parameters in the hydraulic design of a high-speed electrical submersible pump (ESP). In this paper, an ESP with a rotating speed of 6000 r/min was taken as the research object. [...] Read more.

The end clearance of the impeller is one of the most important structural parameters in the hydraulic design of a high-speed electrical submersible pump (ESP). In this paper, an ESP with a rotating speed of 6000 r/min was taken as the research object. Numerical calculations were carried out for five different end clearance conditions of 0.1 mm, 0.3 mm, 0.6 mm, 0.9 mm, and 1.2 mm, respectively, to obtain the performance and internal flow field under different situation. The simulation results were verified by the pump performance experiment. It showed that the increase of the end clearance led to a decrease of the head and efficiency of the electrical submersible pump. Through the analysis of the internal flow field, it was found that the existence of the end clearance reduced the flow rate and caused free pre-whirl. With the increase of the end clearance, the phenomenon of de-flow in the diffuser passage was aggravated, which further reduced the performance of the electrical submersible pump. Finally, the reasonable recommended value of the end clearance was given, which facilitated the optimization design and engineering application of the high-speed ESP. Full article

(This article belongs to the Special Issue Hydraulic Dynamic Calculation and Simulation)

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12 pages, 897 KiB

Open AccessEditor’s ChoiceArticle

Polyhydroxyalkanoates (PHAs) Production: A Feasible Economic Option for the Treatment of Sewage Sludge in Municipal Wastewater Treatment Plants?

by Dafne Crutchik, Oscar Franchi, Luis Caminos, David Jeison, Marisol Belmonte, Alba Pedrouso, Angeles Val del Rio, Anuska Mosquera-Corral and José Luis Campos

Water 2020, 12(4), 1118; https://doi.org/10.3390/w12041118 - 14 Apr 2020

Cited by 100 | Viewed by 17269

Abstract

Sludge is a by-product of municipal wastewater treatment plants (WWTPs) and its management contributes significantly to the operating costs. Large WWTPs usually have anaerobic sludge digesters to valorize sludge as methane and to reduce its mass. However, the low methane market price opens [...] Read more.

Sludge is a by-product of municipal wastewater treatment plants (WWTPs) and its management contributes significantly to the operating costs. Large WWTPs usually have anaerobic sludge digesters to valorize sludge as methane and to reduce its mass. However, the low methane market price opens the possibility for generating other high value-added products from the organic matter in sludge, such as polyhydroxyalkanoates (PHAs). In this work, the economic feasibility of retrofitting two types of WWTPs to convert them into biofactories of crude PHAs was studied. Two cases were analyzed: (a) a large WWTP with anaerobic sludge digestion; and (b) a small WWTP where sludge is only dewatered. In a two-stage PHA-production system (biomass enrichment plus PHAs accumulation), the minimum PHAs cost would be 1.26 and 2.26 US$/kg PHA-crude for the large and small WWTPs, respectively. In a single-stage process, where a fraction of the secondary sludge (25%) is directly used to accumulate PHAs, the production costs would decrease by around 15.9% (small WWTPs) and 19.0% (large WWTPs), since capital costs associated with bioreactors decrease. Sensitivity analysis showed that the PHA/COD (Chemical Oxygen Demand) yield is the most crucial parameter affecting the production costs. The energy, methane, and sludge management prices also have an essential effect on the production costs, and their effect depends on the WWTP’s size. Full article

(This article belongs to the Special Issue Sewage Sludge Treatment and Reuse)

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16 pages, 9853 KiB

Open AccessEditor’s ChoiceArticle

Tracking Lake and Reservoir Changes in the Nenjiang Watershed, Northeast China: Patterns, Trends, and Drivers

by Baojia Du, Zongming Wang, Dehua Mao, Huiying Li and Hengxing Xiang

Water 2020, 12(4), 1108; https://doi.org/10.3390/w12041108 - 13 Apr 2020

Cited by 10 | Viewed by 3598

Abstract

In terms of evident climate change and human activities, investigating changes in lakes and reservoirs is critical for sustainable protection of water resources and ecosystem management over the Nenjiang watershed (NJW), an eco-sensitive semi-arid region and the third-largest inland waterbody cluster in China. [...] Read more.

In terms of evident climate change and human activities, investigating changes in lakes and reservoirs is critical for sustainable protection of water resources and ecosystem management over the Nenjiang watershed (NJW), an eco-sensitive semi-arid region and the third-largest inland waterbody cluster in China. In this study, we established a multi-temporal dataset documenting lake and reservoir (area ≥ 1 km²) changes in this region using an object-oriented image classification method and Landsat series images from 1980 to 2015. Using the structural equation model (SEM), we analyzed the diverse impacts of climatic and anthropogenic variables on lake changes. Results indicated that lakes experienced significant changes with fluctuations over the past 35 years including obvious declines in the total area (by 42%) and number (by 51%) from 1980 to 2010 and a slight increase in the total lake area and number from 2010 to 2015. More than 235 lakes in the size class of 1–10 km² decreased to small lakes (area < 1 km²), while 59 lakes covering 243.75 km² disappeared. Total reservoir area and number had continuous increases during the investigated 35 years, with an areal expansion of 54.9% from 919 km² to 1422 km², and a number increase by 65.3% from 78 to 129. The SEM revealed that the lake area in the NJW had a significant correlation with the mean annual precipitation (MAP), suggesting that the MAP decline clarified most of the lake shrinkage in the NJW. Furthermore, agricultural consumption of water had potential impacts on lake changes, suggested by the significant relationship between cropland area and lake area. Full article

(This article belongs to the Special Issue Impacts of Anthropogenic Activities on Watersheds in a Changing Climate)

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27 pages, 10697 KiB

Open AccessEditor’s ChoiceArticle

Dam Breach Size Comparison for Flood Simulations. A HEC-RAS Based, GIS Approach for Drăcșani Lake, Sitna River, Romania

by Liviu-Marian Albu, Andrei Enea, Marina Iosub and Iuliana-Gabriela Breabăn

Water 2020, 12(4), 1090; https://doi.org/10.3390/w12041090 - 12 Apr 2020

Cited by 41 | Viewed by 9100

Abstract

Floods are the most destructive natural phenomenon, by the total number of casualties, and value of property damage, compared to any other type of natural disaster. However, some of the most destructive flash floods are related to dam breaches or complete collapses, that [...] Read more.

Floods are the most destructive natural phenomenon, by the total number of casualties, and value of property damage, compared to any other type of natural disaster. However, some of the most destructive flash floods are related to dam breaches or complete collapses, that release the large amounts of water, affecting inhabited areas. Worldwide, numerous dams have almost reached or surpassed the estimated construction life span, and pose an increasing risk to structure stability. Considering their continuous degrading state, increasing rainfall aggressiveness, due to climatic changes, technical error, or even human error, there are numerous, potential causes, for which dams could develop breaches and completely fail. This study aims to portray a comparative perspective of flood impact, with real-life consequences, measured by quantifiable parameters, generated from computer simulations of different breach sizes. These parameters include the total flooded surface, water velocity, maximum water depth, number of affected buildings, etc. The analysis was undergone by means of HEC-RAS based 2D hydraulic modeling and GIS, depending on high-accuracy Lidar terrain data and historical hydrological data. As a case study, Drăcșani Lake with the associated Sulița earthfill embankment dam was chosen, being one of the largest and oldest artificial lakes in Romania. Full article

(This article belongs to the Section Hydrology)

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28 pages, 11729 KiB

Open AccessEditor’s ChoiceArticle

Response of Salt Transport and Residence Time to Geomorphologic Changes in an Estuarine System

by Wen-Cheng Liu, Min-Hsin Ke and Hong-Ming Liu

Water 2020, 12(4), 1091; https://doi.org/10.3390/w12041091 - 12 Apr 2020

Cited by 10 | Viewed by 3325

Abstract

Anthropogenic changes in tidal estuaries have significantly altered bathymetry and topography over the past half century. The geomorphic-driven changes in estuarine hydrodynamics and salt transport remain unclear. To explore this issue, a SELFE (Semi-implicit Eulaerian-Lagrangian Finite Element) -based model was developed and utilized [...] Read more.

Anthropogenic changes in tidal estuaries have significantly altered bathymetry and topography over the past half century. The geomorphic-driven changes in estuarine hydrodynamics and salt transport remain unclear. To explore this issue, a SELFE (Semi-implicit Eulaerian-Lagrangian Finite Element) -based model was developed and utilized in a case study in the Danshui River, Taiwan. The model was calibrated and validated using observed water level, current, and salinity data from 2015, 2016, and 2017. The performance of the SELFE model corresponded well to the measured data. Furthermore, the validated model was utilized to analyze the hydrodynamics, residual current, limit of salt intrusion, and residence time under the predevelopment (1981) and present (2015) conditions. The predicted results revealed that the time lag of water surface elevation at both high tide and low tide under the present condition was approximately 0.5–2 h shorter under the predevelopment condition. The residual circulation under the predevelopment condition was stronger than under the present condition for low flow, causing the limit of salt intrusion to extend further upstream under the predevelopment condition compared to the limit of salt intrusion under the present condition. The calculated residence time under the predevelopment condition was longer than the residence time under the present condition. The freshwater discharge input is a dominating factor affecting the salt intrusion and residence time in a tidal estuary. A regression correlation between the maximum distance of salt intrusion and freshwater discharge and a correlation between residence time and freshwater discharge were established to predict the limit of salt intrusion and residence time under the predevelopment and present conditions with different scenarios of freshwater discharge input. Full article

(This article belongs to the Special Issue Hydrodynamics in Estuaries and Coast: Analysis and Modeling)

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13 pages, 2380 KiB

Open AccessEditor’s ChoiceArticle

Lag Times as Indicators of Hydrological Mechanisms Responsible for NO₃-N Flushing in a Forested Headwater Catchment

by Klaudija Sapač, Andrej Vidmar, Nejc Bezak and Simon Rusjan

Water 2020, 12(4), 1092; https://doi.org/10.3390/w12041092 - 12 Apr 2020

Cited by 2 | Viewed by 4408

Abstract

Understanding the temporal variability of the nutrient transport from catchments is essential for planning nutrient loss reduction measures related to land use and climate change. Moreover, observations and analysis of nutrient dynamics in streams draining undisturbed catchments are known to represent a reference [...] Read more.

Understanding the temporal variability of the nutrient transport from catchments is essential for planning nutrient loss reduction measures related to land use and climate change. Moreover, observations and analysis of nutrient dynamics in streams draining undisturbed catchments are known to represent a reference point by which human-influenced catchments can be compared. In this paper, temporal dynamics of nitrate-nitrogen (NO₃-N) flux are investigated on an event basis by analysing observed lag times between data series. More specifically, we studied lag times between the centres of mass of six hydrological and biogeochemical variables, namely discharge, soil moisture at three depths, NO₃-N flux, and the precipitation hyetograph centre of mass. Data obtained by high-frequency measurements (20 min time step) from 29 events were analysed. Linear regression and multiple linear regression (MLR) were used to identify relationships between lag times of the above-mentioned processes. We found that discharge lag time (LAG_Q) and NO₃-N flux lag time (LAG_N) are highly correlated indicating similar temporal response to rainfall. Moreover, relatively high correlation between LAG_N and soil moisture lag times was also detected. The MLR model showed that the most descriptive variable for both LAG_N and LAG_Q is amount of precipitation. For LAG_N, the change of the soil moisture in the upper two layers was also significant, suggesting that the lag times indicate the primarily role of the forest soils as the main source of the NO₃-N flux, whereas the precipitation amount and the runoff formation through the forest soils are the main controlling mechanisms. Full article

(This article belongs to the Special Issue Hydrological Processes in Small Catchments—Runoff and Sediment Yield in Changing Environment)

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21 pages, 4243 KiB

Open AccessEditor’s ChoiceArticle

On the Use of an IoT Integrated System for Water Quality Monitoring and Management in Wastewater Treatment Plants

by Ramón Martínez, Nuria Vela, Abderrazak el Aatik, Eoin Murray, Patrick Roche and Juan M. Navarro

Water 2020, 12(4), 1096; https://doi.org/10.3390/w12041096 - 12 Apr 2020

Cited by 109 | Viewed by 15171

Abstract

The deteriorating water environment demands new approaches and technologies to achieve sustainable and smart management of urban water systems. Wireless sensor networks represent a promising technology for water quality monitoring and management. The use of wireless sensor networks facilitates the improvement of current [...] Read more.

The deteriorating water environment demands new approaches and technologies to achieve sustainable and smart management of urban water systems. Wireless sensor networks represent a promising technology for water quality monitoring and management. The use of wireless sensor networks facilitates the improvement of current centralized systems and traditional manual methods, leading to decentralized smart water quality monitoring systems adaptable to the dynamic and heterogeneous water distribution infrastructure of cities. However, there is a need for a low-cost wireless sensor node solution on the market that enables a cost-effective deployment of this new generation of systems. This paper presents the integration to a wireless sensor network and a preliminary validation in a wastewater treatment plant scenario of a low-cost water quality monitoring device in the close-to-market stage. This device consists of a nitrate and nitrite analyzer based on a novel ion chromatography detection method. The analytical device is integrated using an Internet of Things software platform and tested under real conditions. By doing so, a decentralized smart water quality monitoring system that is conceived and developed for water quality monitoring and management is accomplished. In the presented scenario, such a system allows online near-real-time communication with several devices deployed in multiple water treatment plants and provides preventive and data analytics mechanisms to support decision making. The results obtained comparing laboratory and device measured data demonstrate the reliability of the system and the analytical method implemented in the device. Full article

(This article belongs to the Special Issue Smart Urban Water Networks)

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19 pages, 5589 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Insights into the Photocatalytic Bacterial Inactivation by Flower-Like Bi₂WO₆ under Solar or Visible Light, Through in Situ Monitoring and Determination of Reactive Oxygen Species (ROS)

by Minoo Karbasi, Fathallah Karimzadeh, Keyvan Raeissi, Sami Rtimi, John Kiwi, Stefanos Giannakis and Cesar Pulgarin

Water 2020, 12(4), 1099; https://doi.org/10.3390/w12041099 - 12 Apr 2020

Cited by 42 | Viewed by 5162

Abstract

This study addresses the visible light-induced bacterial inactivation kinetics over a Bi₂WO₆ synthesized catalyst. The systematic investigation was undertaken with Bi₂WO₆ prepared by the complexation of Bi with acetic acid (carboxylate) leading to a flower-like morphology. The [...] Read more.

This study addresses the visible light-induced bacterial inactivation kinetics over a Bi₂WO₆ synthesized catalyst. The systematic investigation was undertaken with Bi₂WO₆ prepared by the complexation of Bi with acetic acid (carboxylate) leading to a flower-like morphology. The characterization of the as-prepared Bi₂WO₆ was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), specific surface area (SSA), and photoluminescence (PL). Under low intensity solar light (<48 mW/cm²), complete bacterial inactivation was achieved within two hours in the presence of the flower-like Bi₂WO₆, while under visible light, the synthesized catalyst performed better than commercial TiO₂. The in situ interfacial charge transfer and local pH changes between Bi₂WO₆ and bacteria were monitored during the bacterial inactivation. Furthermore, the reactive oxygen species (ROS) were identified during Escherichia coli inactivation mediated by appropriate scavengers. The ROS tests alongside the morphological characteristics allowed the proposition of the mechanism for bacterial inactivation. Finally, recycling of the catalyst confirmed the stable nature of the catalyst presented in this study. Full article

(This article belongs to the Special Issue Urban and Industrial Wastewater Disinfection and Decontamination by Advanced Oxidation Processes (AOPs): Current Issues and Future Trends)

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11 pages, 1940 KiB

Open AccessEditor’s ChoiceArticle

Microplastics Removal from Treated Wastewater by a Biofilter

by Fan Liu, Nadia B. Nord, Kai Bester and Jes Vollertsen

Water 2020, 12(4), 1085; https://doi.org/10.3390/w12041085 - 11 Apr 2020

Cited by 98 | Viewed by 13838

Abstract

Microplastic (MP) pollution is a global environmental issue, and traditionally treated wastewater has been identified as a source of land-based microplastics into the aquatic environment. This study evaluated the performance of a pilot-scale biofilter to polish wastewater treatment plant (WWTP) effluent before it [...] Read more.

Microplastic (MP) pollution is a global environmental issue, and traditionally treated wastewater has been identified as a source of land-based microplastics into the aquatic environment. This study evaluated the performance of a pilot-scale biofilter to polish wastewater treatment plant (WWTP) effluent before it enters the environment. The filter was divided into four zones, allowing the concentration of microplastics to be followed through the filter. It was fed with secondary effluent from a conventional WWTP in Denmark. The raw effluent from the WWTP contained 917 items m⁻³ which corresponded to a mass concentration of 24.8 µg m⁻³. After the top layer of the biofilter, the concentration had decreased to a median value of 197 item m⁻³ and 2.8 µg m⁻³, indicating an overall removal efficiency of 79% in terms of particle number and 89% in terms of particle mass. We also observed a tendency that MP of larger size and higher particle mass were more likely to be retained. After the last filtration zone, all MP larger than 100 µm had been removed. The results of this study demonstrate that biofilters are able to lower the MP abundance in treated wastewater significantly, but a complete removal is not ensured, hence some MP, particularly small-sized ones, can still be discharged into the receiving environment. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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23 pages, 377 KiB

Open AccessEditor’s ChoiceReview

Use of Ultrasound as an Advanced Oxidation Process for the Degradation of Emerging Pollutants in Water

by Ana L. Camargo-Perea, Ainhoa Rubio-Clemente and Gustavo A. Peñuela

Water 2020, 12(4), 1068; https://doi.org/10.3390/w12041068 - 9 Apr 2020

Cited by 91 | Viewed by 6876

Abstract

Emerging pollutants are compounds of increased environmental importance and, as such there is interest among researchers in the evaluation of their presence, continuity and elimination in different environmental matrices. The present work reviews the available scientific data on the degradation of emerging pollutants, [...] Read more.

Emerging pollutants are compounds of increased environmental importance and, as such there is interest among researchers in the evaluation of their presence, continuity and elimination in different environmental matrices. The present work reviews the available scientific data on the degradation of emerging pollutants, mainly pharmaceuticals, through ultrasound, as an advanced oxidation process (AOP). This study analyzes the influence of several parameters, such as the nature of the pollutant, the ultrasonic frequency, the electrical power, the pH, the constituents of the matrix and the temperature of the solution on the efficiency of this AOP through researches previously reported in the literature. Additionally, it informs on the application of the referred process alone and/or in combination with other AOPs focusing on the treatment of domestic and industrial wastewaters containing emerging pollutants, mainly pharmaceuticals, as well as on the economic costs associated with and the future perspectives that make ultrasound a possible candidate to solve the problem of water pollution by these emerging pollutants.. Full article

(This article belongs to the Special Issue Urban and Industrial Wastewater Disinfection and Decontamination by Advanced Oxidation Processes (AOPs): Current Issues and Future Trends)

16 pages, 7431 KiB

Open AccessEditor’s ChoiceArticle

Simulating the Hydraulic Heave Phenomenon with Multiphase Fluid Flows Using CFD-DEM

by Qiong Xiao

Water 2020, 12(4), 1077; https://doi.org/10.3390/w12041077 - 9 Apr 2020

Cited by 3 | Viewed by 3323

Abstract

In geotechnical engineering, the seepage phenomena, especially regarding the hydraulic heave, is one of the most dangerous failure mechanisms related to infrastructural stability. Hence, a fundamental understanding of this occurrence is important for the design and construction of water-retaining structures. In this study, [...] Read more.

In geotechnical engineering, the seepage phenomena, especially regarding the hydraulic heave, is one of the most dangerous failure mechanisms related to infrastructural stability. Hence, a fundamental understanding of this occurrence is important for the design and construction of water-retaining structures. In this study, a computational fluid dynamics (CFD) solver was developed and coupled with discrete element method (DEM) software to simulate the seepage failure process for the three phases of soil, water, and air. Specimens were constructed with two layers of gap-graded particles to give different permeability properties in the vertical direction. More significant heave failure was observed for the sample with higher permeability in the upper layer. Special attention was drawn to the particle-scale observations of the internal structure and drag force to study the erosion mechanism. The soil filled with air bubbles produced a higher drag force in the region below the retaining wall and showed a larger loss of fine particles than the saturated soil, particularly in the initial stages. The results indicate that the impact of air bubbles would accelerate the development of the heave or boiling phenomenon and influence the stability of the system at an early stage. Full article

(This article belongs to the Special Issue Granular Flows Modeling and Simulation)

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17 pages, 639 KiB

Open AccessEditor’s ChoiceArticle

A Rentier State under Blockade: Qatar’s Water-Energy-Food Predicament from Energy Abundance and Food Insecurity to a Silent Water Crisis

by Hussam Hussein and Laurent A. Lambert

Water 2020, 12(4), 1051; https://doi.org/10.3390/w12041051 - 8 Apr 2020

Cited by 28 | Viewed by 15955

Abstract

This article investigates Qatar’s sustainability crisis of the high levels of water, electricity and food use. The high levels of consumption have been enabled by Qatar’s significant hydrocarbons wealth, a generous rentier state’s redistributive water governance, and structural dependence on imported food and [...] Read more.

This article investigates Qatar’s sustainability crisis of the high levels of water, electricity and food use. The high levels of consumption have been enabled by Qatar’s significant hydrocarbons wealth, a generous rentier state’s redistributive water governance, and structural dependence on imported food and food production subsidies. The water crisis is silent because it does not generate supply disruptions nor any public discontentment. The geopolitical blockade Qatar is experiencing sparked discussions in policy circles on the best ways to ensure food security, but has only exacerbated its water insecurity. The blockade makes more urgent than ever the necessity to maximize and increase synergies among different sectors. Full article

(This article belongs to the Section Water, Agriculture and Aquaculture)

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14 pages, 1654 KiB

Open AccessEditor’s ChoiceArticle

Living at the Water’s Edge: A World-Wide Econometric Panel Estimation of Arable Water Footprint Drivers

by Pilar Gracia-de-Rentería, George Philippidis, Hugo Ferrer-Pérez and Ana Isabel Sanjuán

Water 2020, 12(4), 1060; https://doi.org/10.3390/w12041060 - 8 Apr 2020

Cited by 4 | Viewed by 3335

Abstract

As part of the Sustainable Development Goal (SDG) for ensuring clean water and sanitation worldwide by 2030, SDG target 6.4 seeks to attain sustainable withdrawals of freshwater through efficiency gains with a view to relieving water stress in vulnerable populated areas. The water [...] Read more.

As part of the Sustainable Development Goal (SDG) for ensuring clean water and sanitation worldwide by 2030, SDG target 6.4 seeks to attain sustainable withdrawals of freshwater through efficiency gains with a view to relieving water stress in vulnerable populated areas. The water footprint (WF) is a key metric to measure this concept, although the dynamics of the drivers of the WF through space and time remain relatively under-researched, whilst in foresight studies, the WF is often subject to simplistic assumptions. Thus, constructing a panel dataset of 130 countries and 156 crops for the period 2002–2016, this paper empirically assesses the sign and magnitude of WF drivers of agricultural crop activities, employing a careful selection of demographic, economic and climatic drivers. The study uncovers evidence of significant deviations in WF drivers across regions segmented by relative wealth, relating specifically to the stage of economic development and the presence (absence) of economies of scale, whilst we confirm that geographical coordinates have a major bearing on the climatic WF driver. Moreover, examining the temporal dimension, there is compelling evidence supporting a structural break in the role that technical progress exerted on the WF prior to, and in the wake of, the 2008 financial crisis. Full article

(This article belongs to the Special Issue Virtual Water Trade and Water Resources Economics)

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15 pages, 4595 KiB

Open AccessEditor’s ChoiceArticle

Removal of Pharmaceuticals, Toxicity and Natural Fluorescence by Ozonation in Biologically Pre-Treated Municipal Wastewater, in Comparison to Subsequent Polishing Biofilm Reactors

by Kai Tang, Gordon T. H. Ooi, Aikaterini Spiliotopoulou, Kamilla M. S. Kaarsholm, Kim Sundmark, Bianca Florian, Caroline Kragelund, Kai Bester and Henrik R. Andersen

Water 2020, 12(4), 1059; https://doi.org/10.3390/w12041059 - 8 Apr 2020

Cited by 9 | Viewed by 4227

Abstract

Ozonation followed by a polishing moving bed biofilm reactor (MBBR) was implemented in pilot and laboratory to remove the residual pharmaceuticals and toxicity from wastewater effluent, which was from a pilot hybrid system of MBBR and activated sludge, receiving municipal wastewater. The delivered [...] Read more.

Ozonation followed by a polishing moving bed biofilm reactor (MBBR) was implemented in pilot and laboratory to remove the residual pharmaceuticals and toxicity from wastewater effluent, which was from a pilot hybrid system of MBBR and activated sludge, receiving municipal wastewater. The delivered ozone dosages achieving 90% pharmaceutical removal were determined both in pilot and laboratory experiments and they were normalised to dissolved organic carbon (DOC), illustrating our findings were comparable with previously published literature. During wastewater ozonation, the intensity of natural fluorescence was found to be greatly associated with the concentrations of the studied pharmaceuticals. In pilot experiments, toxicity, measured by Vibrio fischeri, increased after ozonation at delivered ozone dosages at 0.38–0.47 mg O₃/mg DOC and was completely removed by the subsequent polishing MBBR. Laboratory experiments verified that the polishing MBBR was able to remove the toxicity produced by the ozonation. Full article

(This article belongs to the Special Issue Hybrid Systems Using Different Technologies for Wastewater Treatment and Reuse)

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18 pages, 6766 KiB

Open AccessEditor’s ChoiceArticle

Sociohydrologic Systems Thinking: An Analysis of Undergraduate Students’ Operationalization and Modeling of Coupled Human-Water Systems

by Diane Lally and Cory T. Forbes

Water 2020, 12(4), 1040; https://doi.org/10.3390/w12041040 - 7 Apr 2020

Cited by 15 | Viewed by 4332

Abstract

One of the keys to science and environmental literacy is systems thinking. Learning how to think about the interactions between systems, the far-reaching effects of a system, and the dynamic nature of systems are all critical outcomes of science learning. However, students need [...] Read more.

One of the keys to science and environmental literacy is systems thinking. Learning how to think about the interactions between systems, the far-reaching effects of a system, and the dynamic nature of systems are all critical outcomes of science learning. However, students need support to develop systems thinking skills in undergraduate geoscience classrooms. While systems thinking-focused instruction has the potential to benefit student learning, gaps exist in our understanding of students’ use of systems thinking to operationalize and model SHS, as well as their metacognitive evaluation of systems thinking. To address this need, we have designed, implemented, refined, and studied an introductory-level, interdisciplinary course focused on coupled human-water, or sociohydrologic, systems. Data for this study comes from three consecutive iterations of the course and involves student models and explanations for a socio-hydrologic issue (n = 163). To analyze this data, we counted themed features of the drawn models and applied an operationalization rubric to the written responses. Analyses of the written explanations reveal statistically-significant differences between underlying categories of systems thinking (F(5, 768) = 401.6, p < 0.05). Students were best able to operationalize their systems thinking about problem identification (M = 2.22, SD = 0.73) as compared to unintended consequences (M = 1.43, SD = 1.11). Student-generated systems thinking models revealed statistically significant differences between system components, patterns, and mechanisms, F(2, 132) = 3.06, p < 0.05. Students focused most strongly on system components (M = 13.54, SD = 7.15) as compared to related processes or mechanisms. Qualitative data demonstrated three types of model limitation including scope/scale, temporal, and specific components/mechanisms/patterns excluded. These findings have implications for supporting systems thinking in undergraduate geoscience classrooms, as well as insight into links between these two skills. Full article

(This article belongs to the Special Issue Water Literacy and Education)

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30 pages, 17371 KiB

Open AccessEditor’s ChoiceReview

Recent Trends in Removal Pharmaceuticals and Personal Care Products by Electrochemical Oxidation and Combined Systems

by Khanh Chau Dao, Chih-Chi Yang, Ku-Fan Chen and Yung-Pin Tsai

Water 2020, 12(4), 1043; https://doi.org/10.3390/w12041043 - 7 Apr 2020

Cited by 50 | Viewed by 7060

Abstract

Due to various potential toxicological threats to living organisms even at low concentrations, pharmaceuticals and personal care products in natural water are seen as an emerging environmental issue. The low efficiency of removal of pharmaceuticals and personal care products by conventional wastewater treatment [...] Read more.

Due to various potential toxicological threats to living organisms even at low concentrations, pharmaceuticals and personal care products in natural water are seen as an emerging environmental issue. The low efficiency of removal of pharmaceuticals and personal care products by conventional wastewater treatment plants calls for more efficient technology. Research on advanced oxidation processes has recently become a hot topic as it has been shown that these technologies can effectively oxidize most organic contaminants to inorganic carbon through mineralization. Among the advanced oxidation processes, the electrochemical advanced oxidation processes and, in general, electrochemical oxidation or anodic oxidation have shown good prospects at the lab-scale for the elimination of contamination caused by the presence of residual pharmaceuticals and personal care products in aqueous systems. This paper reviewed the effectiveness of electrochemical oxidation in removing pharmaceuticals and personal care products from liquid solutions, alone or in combination with other treatment processes, in the last 10 years. Reactor designs and configurations, electrode materials, operational factors (initial concentration, supporting electrolytes, current density, temperature, pH, stirring rate, electrode spacing, and fluid velocity) were also investigated. Full article

(This article belongs to the Special Issue Advanced Oxidation Processes for Water and Wastewater Treatment)

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19 pages, 1853 KiB

Open AccessEditor’s ChoiceReview

Drinking Water Temperature around the Globe: Understanding, Policies, Challenges and Opportunities

by Claudia Agudelo-Vera, Stefania Avvedimento, Joby Boxall, Enrico Creaco, Henk de Kater, Armando Di Nardo, Aleksandar Djukic, Isabel Douterelo, Katherine E. Fish, Pedro L. Iglesias Rey, Nenad Jacimovic, Heinz E. Jacobs, Zoran Kapelan, Javier Martinez Solano, Carolina Montoya Pachongo, Olivier Piller, Claudia Quintiliani, Jan Ručka, Ladislav Tuhovčák and Mirjam Blokker

Water 2020, 12(4), 1049; https://doi.org/10.3390/w12041049 - 7 Apr 2020

Cited by 97 | Viewed by 19429

Abstract

Water temperature is often monitored at water sources and treatment works; however, there is limited monitoring of the water temperature in the drinking water distribution system (DWDS), despite a known impact on physical, chemical and microbial reactions which impact water quality. A key [...] Read more.

Water temperature is often monitored at water sources and treatment works; however, there is limited monitoring of the water temperature in the drinking water distribution system (DWDS), despite a known impact on physical, chemical and microbial reactions which impact water quality. A key parameter influencing drinking water temperature is soil temperature, which is influenced by the urban heat island effects. This paper provides critique and comprehensive summary of the current knowledge, policies and challenges regarding drinking water temperature research and presents the findings from a survey of international stakeholders. Knowledge gaps as well as challenges and opportunities for monitoring and research are identified. The conclusion of the study is that temperature in the DWDS is an emerging concern in various countries regardless of the water source and treatment, climate conditions, or network characteristics such as topology, pipe material or diameter. More research is needed, especially to determine (i) the effect of higher temperatures, (ii) a legislative limit on temperature and (iii) measures to comply with this limit. Full article

(This article belongs to the Special Issue Water Quality in Drinking Water Distribution Systems)

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20 pages, 5756 KiB

Open AccessEditor’s ChoiceArticle

Climate Change Impact on Surface Water and Groundwater Recharge in Northern Thailand

by Chanchai Petpongpan, Chaiwat Ekkawatpanit and Duangrudee Kositgittiwong

Water 2020, 12(4), 1029; https://doi.org/10.3390/w12041029 - 4 Apr 2020

Cited by 34 | Viewed by 9438

Abstract

Climate change is progressing and is now one of the most important global challenges for humanities. Water resources management is one of the key challenges to reduce disaster risk. In Northern Thailand, flood and drought have always occurred because of the climate change [...] Read more.

Climate change is progressing and is now one of the most important global challenges for humanities. Water resources management is one of the key challenges to reduce disaster risk. In Northern Thailand, flood and drought have always occurred because of the climate change impact and non-systematic management in the conjunctive use of both sources of water. Therefore, this study aims to assess the climate change impact on surface water and groundwater of the Yom and Nan river basins, located in the upper part of Thailand. The surface water and groundwater regimes are generated by a fully coupled SWAT-MODFLOW model. The future climate scenarios are considered from the Representative Concentration Pathways (RCPs) 2.6 and 8.5, presented by the Coupled Model Intercomparison Project Phase 5 (CMIP5), in order to mainly focus on the minimum and maximum Green House Gas (GHG) emissions scenarios during the near future (2021–2045) periods. The results show that the average annual air temperature rises by approximately 0.5–0.6 °C and 0.9–1.0 °C under the minimum (RCP 2.6) and maximum (RCP 8.5) GHG emission scenarios, respectively. The annual rainfall, obtained from both scenarios, increased by the same range of 20–200 mm/year, on average. The summation of surface water (water yield) and groundwater recharge (water percolation) in the Yom river basin decreased by 443.98 and 316.77 million m³/year under the RCPs 2.6 and 8.5, respectively. While, in the Nan river basin, it is projected to increase by 355 million m³/year under RCP 2.6 but decrease by 20.79 million m³/year under RCP 8.5. These quantitative changes can directly impact water availability when evaluating the water demand for consumption, industry, and agriculture. Full article

(This article belongs to the Special Issue Modeling Global Change Impacts on Water Resources: Selected Papers from the 2019/2020 SWAT International Conferences)

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18 pages, 3063 KiB

Open AccessEditor’s ChoiceArticle

Assessing Inhomogeneities in Extreme Annual Rainfall Data Series by Multifractal Approach

by Amanda P. García-Marín, Javier Estévez, Renato Morbidelli, Carla Saltalippi, José Luis Ayuso-Muñoz and Alessia Flammini

Water 2020, 12(4), 1030; https://doi.org/10.3390/w12041030 - 4 Apr 2020

Cited by 16 | Viewed by 3792

Abstract

Testing the homogeneity in extreme rainfall data series is an important step to be performed before applying the frequency analysis method to obtain quantile values. In this work, six homogeneity tests were applied in order to check the existence of break points in [...] Read more.

Testing the homogeneity in extreme rainfall data series is an important step to be performed before applying the frequency analysis method to obtain quantile values. In this work, six homogeneity tests were applied in order to check the existence of break points in extreme annual 24-h rainfall data at eight stations located in the Umbria region (Central Italy). Two are parametric tests (the standard normal homogeneity test and Buishand test) whereas the other four are non-parametric (the Pettitt, Sequential Mann–Kendal, Mann–Whitney U, and Cumulative Sum tests). No break points were detected at four of the stations analyzed. Where inhomogeneities were found, the multifractal approach was applied in order to check if they were real or not by comparing the split and whole data series. The generalized fractal dimension functions D_q and the multifractal spectra f(α) were obtained, and their main parameters were used to decide whether or not a break point existed. Full article

(This article belongs to the Section Hydrology)

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27 pages, 4380 KiB

Open AccessEditor’s ChoiceArticle

Tree-Based Modeling Methods to Predict Nitrate Exceedances in the Ogallala Aquifer in Texas

by Venkatesh Uddameri, Ana Luiza Bessa Silva, Sreeram Singaraju, Ghazal Mohammadi and E. Annette Hernandez

Water 2020, 12(4), 1023; https://doi.org/10.3390/w12041023 - 3 Apr 2020

Cited by 25 | Viewed by 4671

Abstract

The performance of four tree-based classification techniques—classification and regression trees (CART), multi-adaptive regression splines (MARS), random forests (RF) and gradient boosting trees (GBT) were compared against the commonly used logistic regression (LR) analysis to assess aquifer vulnerability in the Ogallala Aquifer of Texas. [...] Read more.

The performance of four tree-based classification techniques—classification and regression trees (CART), multi-adaptive regression splines (MARS), random forests (RF) and gradient boosting trees (GBT) were compared against the commonly used logistic regression (LR) analysis to assess aquifer vulnerability in the Ogallala Aquifer of Texas. The results indicate that the tree-based models performed better than the logistic regression model, as they were able to locally refine nitrate exceedance probabilities. RF exhibited the best generalizable capabilities. The CART model did better in predicting non-exceedances. Nitrate exceedances were sensitive to well depths—an indicator of aquifer redox conditions, which, in turn, was controlled by alkalinity increases brought forth by the dissolution of calcium carbonate. The clay content of soils and soil organic matter, which serve as indicators of agriculture activities, were also noted to have significant influences on nitrate exceedances. Likely nitrogen releases from confined animal feedlot operations in the northeast portions of the study area also appeared to be locally important. Integrated soil, hydrogeological and geochemical datasets, in conjunction with tree-based methods, help elucidate processes controlling nitrate exceedances. Overall, tree-based models offer flexible, transparent approaches for mapping nitrate exceedances, identifying underlying mechanisms and prioritizing monitoring activities. Full article

(This article belongs to the Section Hydrology)

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18 pages, 5670 KiB

Open AccessEditor’s ChoiceArticle

Fluid-Structure Interaction Response of a Water Conveyance System with a Surge Chamber during Water Hammer

by Qiang Guo, Jianxu Zhou, Yongfa Li, Xiaolin Guan, Daohua Liu and Jian Zhang

Water 2020, 12(4), 1025; https://doi.org/10.3390/w12041025 - 3 Apr 2020

Cited by 13 | Viewed by 3545

Abstract

Fluid–structure interaction (FSI) is a frequent and unstable inherent phenomenon in water conveyance systems. Especially in a system with a surge chamber, valve closing and the subsequent water level oscillation in the surge chamber are the excitation source of the hydraulic transient process. [...] Read more.

Fluid–structure interaction (FSI) is a frequent and unstable inherent phenomenon in water conveyance systems. Especially in a system with a surge chamber, valve closing and the subsequent water level oscillation in the surge chamber are the excitation source of the hydraulic transient process. Water-hammer-induced FSI has not been considered in preceding research, and the results without FSI justify further investigations. In this study, an FSI eight-equation model is presented to capture its influence. Both the elbow pipe and surge chamber are treated as boundary conditions, and solved using the finite volume method (FVM). After verifying the feasibility of using FVM to solve FSI, friction, Poisson, and junction couplings are discussed in detail to separately reveal the influence of a surge chamber, tow elbows, and a valve on FSI. Results indicated that the major mechanisms of coupling are junction coupling and Poisson coupling. The former occurs in the surge chamber and elbows. Meanwhile, a stronger pressure pulsation is produced at the valve, resulting in a more complex FSI response in the water conveyance system. Poisson coupling and junction coupling are the main factors contributing to a large amount of local transilience emerging on the dynamic pressure curves. Moreover, frictional coupling leads to the lower amplitudes of transilience. These results indicate that the transilience is induced by the water hammer–structure interaction and plays important roles in the orifice optimization in the surge chamber. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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15 pages, 2187 KiB

Open AccessEditor’s ChoiceArticle

Model Analysis and System Parameters Investigation for Transient Wave in a Pump–Pipe–Valve System

by Zubin Liu, Dingyi Pan, Fengzhong Qu and Jianxin Hu

Water 2020, 12(4), 1014; https://doi.org/10.3390/w12041014 - 2 Apr 2020

Viewed by 2672

Abstract

The frequency responses of the transient wave propagating in a pump–pipe–valve system are studied with the system transfer matrix analysis (STMA) method. Being different to that in the reservoir–pipe–valve system, the transient wave is used as a long-distance communication technology in the pump–pipe–valve [...] Read more.

The frequency responses of the transient wave propagating in a pump–pipe–valve system are studied with the system transfer matrix analysis (STMA) method. Being different to that in the reservoir–pipe–valve system, the transient wave is used as a long-distance communication technology in the pump–pipe–valve system, and very few works have been done on the model analysis and strategies to control the behavior of the oscillation signal of the pipe pressure. The theoretic solutions are studied with three internal friction models: frictionless, steady friction, and unsteady friction. The dimensionless parameter of the valve signal intensity (VSI) is proposed, and it is found to be a key factor affecting the quality of the wave propagation in the pipe. A larger pressure oscillation at the upstream side results when the VSI is smaller than one, whereas a more uniform amplitude for the resonances and anti-resonances is obtained when VSI approaches one. Some feasible suggestions are provided to obtain high quality wave signals. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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18 pages, 8658 KiB

Open AccessEditor’s ChoiceArticle

The Impact of Submerged Breakwaters on Sediment Distribution along Marsh Boundaries

by Iacopo Vona, Matthew W. Gray and William Nardin

Water 2020, 12(4), 1016; https://doi.org/10.3390/w12041016 - 2 Apr 2020

Cited by 34 | Viewed by 8883

Abstract

Human encroachment and development on coastlines have led to greater amounts of armoring of shorelines. Breakwaters are a common feature along coastlines, which are used to dampen wave energy and protect shorelines from flash floods or overwash events. Although common, their effects on [...] Read more.

Human encroachment and development on coastlines have led to greater amounts of armoring of shorelines. Breakwaters are a common feature along coastlines, which are used to dampen wave energy and protect shorelines from flash floods or overwash events. Although common, their effects on sediment transport and marsh geomorphology are poorly understood. To address this gap, our study quantifies the effects of breakwaters on sediment transport and marsh evolution under different wave regimes using Delft3D-SWAN, a dynamic geomorphodynamic numerical model. Model configurations used the same numerical domain, but scenarios had different sediments, waves, tides, basin slopes and breakwater distances from the shoreline to explore how waves and tidal currents shape coastal margins. Model results suggested breakwaters were responsible for an average wave damping between 10–50%, proportional to the significant wave height across all modeled scenarios. Shear stress at the beginning of the marsh and the volume of sediment deposited at the end of the simulation (into the marsh behind the breakwater) increased on average between 20–40%, proportional to the slope and distance of the breakwater from the shoreline. Sediment trapping, defined as the ratio between the volume of sediment housed into the salt marsh behind and away from the breakwater, was found to be less than 1 from most model runs. Study results indicated that breakwaters are advantageous for wave breaking to protect shorelines from the wave’s energy, however, they might also be an obstacle for sediment transport, negatively affecting nourishment processes, and, consequently, impeded long-term salt marsh survival. Identifying a balance between waves dampening and shoreline nourishment should be considered in the design and implementation of these structures. Full article

(This article belongs to the Special Issue Advances in the Study of Coastal Resilience, Hydrodynamic Modelling and Coastal Monitoring)

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15 pages, 5261 KiB

Open AccessEditor’s ChoiceArticle

Differences of Regulative Flexibility between Hydrological Isolated and Connected Lakes in a Large Floodplain: Insight from Inundation Dynamics and Landscape Heterogeneity

by Jiakun Teng, Shaoxia Xia, Yu Liu, Peng Cui, Jiang Chen, Wuwei Si, Houlang Duan and Xiubo Yu

Water 2020, 12(4), 991; https://doi.org/10.3390/w12040991 - 1 Apr 2020

Cited by 14 | Viewed by 3395

Abstract

The inundation areas of floodplains are crucial to wetland ecosystems, especially in supporting biodiversity. Accurately identifying the spatial and temporal patterns of inundation areas is important for understanding floodplain ecosystem processes. Here, lakes in the Yangtze River Floodplain were divided into two types [...] Read more.

The inundation areas of floodplains are crucial to wetland ecosystems, especially in supporting biodiversity. Accurately identifying the spatial and temporal patterns of inundation areas is important for understanding floodplain ecosystem processes. Here, lakes in the Yangtze River Floodplain were divided into two types according to hydrological conditions: the natural connected lakes (Dongting Lake and Poyang Lake) with natural water level fluctuations and the isolated lakes (lakes in Jianghan Plain) with stable water levels. We established a method to identify inundation areas using multi-sources remote sensing data based on the Google Earth Engine. The dynamics of inundation areas were determined, and the relative indices were calculated in common year (2017) and a drought year (2018). The differences between the connected lakes and the isolated lakes were analyzed, and impacts of hydrological fluctuations on inundation area and habitat quality were evaluated. The results show that lakes with natural hydrological fluctuations have a greater regulative flexibility, with both patch density (PD) and submerged elasticity index (SEI) values higher than that of isolated lakes. The trend of the vegetation index in the connected lakes and in the isolated lakes is also different. The mean EVI in Dongting Lake and Poyang Lake showed a U-shaped trend which is similar to the shape of the trend of PD. The trend of mean enhanced vegetation index (EVI) in the isolated lakes is the opposite and has a lower range of variation over a year. This study provides new indicators and rapid methods for habitat quality assessment in floodplains, as well as presenting scientific information useful for improving wetland management in the middle and lower Yangtze River. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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13 pages, 1835 KiB

Open AccessEditor’s ChoiceArticle

Flood Control Versus Water Conservation in Reservoirs: A New Policy to Allocate Available Storage

by Ivan Gabriel-Martin, Alvaro Sordo-Ward, David Santillán and Luis Garrote

Water 2020, 12(4), 994; https://doi.org/10.3390/w12040994 - 1 Apr 2020

Cited by 9 | Viewed by 6139

Abstract

The aim of this study is to contribute to solving conflicts that arise in the operation of multipurpose reservoirs when determining maximum conservation levels (MCLs). The specification of MCLs in reservoirs that are operated for water supply and flood control may imply a [...] Read more.

The aim of this study is to contribute to solving conflicts that arise in the operation of multipurpose reservoirs when determining maximum conservation levels (MCLs). The specification of MCLs in reservoirs that are operated for water supply and flood control may imply a reduction in the volume of water supplied with a pre-defined reliability in the system. The procedure presented in this study consists of the joint optimization of the reservoir yield with a specific reliability subject to constraints imposed by hydrological dam safety and downstream river safety. We analyzed two different scenarios by considering constant or variable initial reservoir level prior to extreme flood events. In order to achieve the global optimum configuration of MCLs for each season, we propose the joint optimization of three variables: minimize the maximum reservoir level (return period of 1000 years), minimize the maximum released outflow (return period of 500 years) and maximize the reservoir yield with 90% reliability. We applied the methodology to Riaño Dam, jointly operated for irrigation and flood control. Improvements in the maximum reservoir yield (with 90% reliability) increased up to 10.1% with respect to the currently supplied annual demand (545 hm³) for the same level of dam and downstream hydrological safety. The improvement could increase up to 26.8% when compared to deterministic procedures. Moreover, dam stakeholders can select from a set of Pareto-optimal configurations depending on if their main emphasis is to maintain/increase the hydrological safety, or rather to maintain/increase the reservoir yield. Full article

(This article belongs to the Special Issue Water Resources Management Models for Policy Assessment)

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26 pages, 25663 KiB

Open AccessEditor’s ChoiceArticle

Symmetrical Rank-Three Vectorized Loading Scores Quasi-Newton for Identification of Hydrogeological Parameters and Spatiotemporal Recharges

by Chien-Lin Huang, Nien-Sheng Hsu, Fu-Jian Hsu, Gene J.-Y. You and Chun-Hao Yao

Water 2020, 12(4), 995; https://doi.org/10.3390/w12040995 - 1 Apr 2020

Viewed by 2862

Abstract

In a multi-layered groundwater model, achieving accurate spatiotemporal identification and solving the ill-posed problem is the vital topic for model calibration. This study proposes a symmetry rank three vectorized loading scores (SR3 VLS) quasi-Newton algorithm by modifying the Levenberg–Marquardt algorithm and importing a [...] Read more.

In a multi-layered groundwater model, achieving accurate spatiotemporal identification and solving the ill-posed problem is the vital topic for model calibration. This study proposes a symmetry rank three vectorized loading scores (SR3 VLS) quasi-Newton algorithm by modifying the Levenberg–Marquardt algorithm and importing a rank three structure from Broyden–Fletcher–Goldfarb–Shanno algorithm for identification of hydrogeological parameters and spatiotemporal recharge simultaneously. To accelerate directional convergence and approach a global optimum, this study uses a vectorized limited switchable step size in the transmissive groundwater inverse problem. The Hessian approximation rank three uses high and low-rank factor loading scores analyzed from simulated storage fluctuation between adjacent iterations for calculation and matrix correction. Two numerical experiments were designed to validate the proposing algorithm, showing the SR3 VLS quasi-Newton reduced the error percentages of the identified parameters by 1.63% and 9.65% compared to the Jacobian quasi-Newton. The proposing method is applied to the Chou-Shui River alluvial fan groundwater system in Taiwan. Results show that the simulated storage error decreased rapidly in six iterations, and has good head convergence as small as 0.11% with a root-mean-square-error (RMSE) of 0.134 m, indicating that the proposing algorithm reduces the computational cost to converge to the true solution. Full article

(This article belongs to the Special Issue Computational Methods in Water Resources)

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29 pages, 4186 KiB

Open AccessEditor’s ChoiceReview

Water Network Partitioning into District Metered Areas: A State-Of-The-Art Review

by Xuan Khoa Bui, Malvin S. Marlim and Doosun Kang

Water 2020, 12(4), 1002; https://doi.org/10.3390/w12041002 - 1 Apr 2020

Cited by 78 | Viewed by 15226

Abstract

A water distribution network (WDN) is an indispensable element of civil infrastructure that provides fresh water for domestic use, industrial development, and fire-fighting. However, in a large and complex network, operation and management (O&M) can be challenging. As a technical initiative to improve [...] Read more.

A water distribution network (WDN) is an indispensable element of civil infrastructure that provides fresh water for domestic use, industrial development, and fire-fighting. However, in a large and complex network, operation and management (O&M) can be challenging. As a technical initiative to improve O&M efficiency, the paradigm of “divide and conquer” can divide an original WDN into multiple subnetworks. Each subnetwork is controlled by boundary pipes installed with gate valves or flow meters that control the water volume entering and leaving what are known as district metered areas (DMAs). Many approaches to creating DMAs are formulated as two-phase procedures, clustering and sectorizing, and are called water network partitioning (WNP) in general. To assess the benefits and drawbacks of DMAs in a WDN, we provide a comprehensive review of various state-of-the-art approaches, which can be broadly classified as: (1) Clustering algorithms, which focus on defining the optimal configuration of DMAs; and (2) sectorization procedures, which physically decompose the network by selecting pipes for installing flow meters or gate valves. We also provide an overview of emerging problems that need to be studied. Full article

(This article belongs to the Special Issue Smart Urban Water Networks)

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18 pages, 4437 KiB

Open AccessEditor’s ChoiceArticle

The Selection of Rain Gauges and Rainfall Parameters in Estimating Intensity-Duration Thresholds for Landslide Occurrence: Case Study from Wayanad (India)

by Minu Treesa Abraham, Neelima Satyam, Ascanio Rosi, Biswajeet Pradhan and Samuele Segoni

Water 2020, 12(4), 1000; https://doi.org/10.3390/w12041000 - 1 Apr 2020

Cited by 51 | Viewed by 9708

Abstract

Recurring landslides in the Western Ghats have become an important concern for authorities, considering the recent disasters that occurred during the 2018 and 2019 monsoons. Wayanad is one of the highly affected districts in Kerala State (India), where landslides have become a threat [...] Read more.

Recurring landslides in the Western Ghats have become an important concern for authorities, considering the recent disasters that occurred during the 2018 and 2019 monsoons. Wayanad is one of the highly affected districts in Kerala State (India), where landslides have become a threat to lives and properties. Rainfall is the major factor which triggers landslides in this region, and hence, an early warning system could be developed based on empirical rainfall thresholds considering the relationship between rainfall events and their potential to initiate landslides. As an initial step in achieving this goal, a detailed study was conducted to develop a regional scale rainfall threshold for the area using intensity and duration conditions, using the landslides that occurred during the years from 2010 to 2018. Detailed analyses were conducted in order to select the most effective method for choosing a reference rain gauge and rainfall event associated with the occurrence of landslides. The study ponders the effect of the selection of rainfall parameters for this data-sparse region by considering four different approaches. First, a regional scale threshold was defined using the nearest rain gauge. The second approach was achieved by selecting the most extreme rainfall event recorded in the area, irrespective of the location of landslide and rain gauge. Third, the classical definition of intensity was modified from average intensity to peak daily intensity measured by the nearest rain gauge. In the last approach, four different local scale thresholds were defined, exploring the possibility of developing a threshold for a uniform meteo-hydro-geological condition instead of merging the data and developing a regional scale threshold. All developed thresholds were then validated and empirically compared to find the best suited approach for the study area. From the analysis, it was observed that the approach selecting the rain gauge based on the most extreme rainfall parameters performed better than the other approaches. The results are useful in understanding the sensitivity of Intensity–Duration threshold models to some boundary conditions such as rain gauge selection, the intensity definition and the strategy of subdividing the area into independent alert zones. The results were discussed with perspective on a future application in a regional scale Landslide Early Warning System (LEWS) and on further improvements needed for this objective. Full article

(This article belongs to the Special Issue Rainfall Thresholds and Other Approaches for Landslide Prediction and Early Warning)

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23 pages, 4109 KiB

Open AccessEditor’s ChoiceArticle

Statistical Evaluation of the Latest GPM-Era IMERG and GSMaP Satellite Precipitation Products in the Yellow River Source Region

by Jiayong Shi, Fei Yuan, Chunxiang Shi, Chongxu Zhao, Limin Zhang, Liliang Ren, Yonghua Zhu, Shanhu Jiang and Yi Liu

Water 2020, 12(4), 1006; https://doi.org/10.3390/w12041006 - 1 Apr 2020

Cited by 41 | Viewed by 5310

Abstract

As the successor of Tropical Rainfall Measuring Mission, Global Precipitation Measurement (GPM) has released a range of satellite-based precipitation products (SPPs). This study conducts a comparative analysis on the quality of the integrated multisatellite retrievals for GPM (IMERG) and global satellite mapping of [...] Read more.

As the successor of Tropical Rainfall Measuring Mission, Global Precipitation Measurement (GPM) has released a range of satellite-based precipitation products (SPPs). This study conducts a comparative analysis on the quality of the integrated multisatellite retrievals for GPM (IMERG) and global satellite mapping of precipitation (GSMaP) SPPs in the Yellow River source region (YRSR). This research includes the eight latest GPM-era SPPs, namely, IMERG “Early,” “Late,” and “Final” run SPPs (IMERG-E, IMERG-L, and IMERG-F) and GSMaP gauge-adjusted product (GSMaP-Gauge), microwave-infrared reanalyzed product (GSMaP-MVK), near-real-time product (GSMaP-NRT), near-real-time product with gauge-based adjustment (GSMaP-Gauge-NRT), and real-time product (GSMaP-NOW). In addition, the IMERG SPPs were compared with GSMaP SPPs at multiple spatiotemporal scales. Results indicate that among the three IMERG SPPs, IMERG-F exhibited the lowest systematic errors and the best quality, followed by IMERG-E and IMERG-L. IMERG-E and IMERG-L underestimated the occurrences of light-rain events but overestimated the moderate and heavy rain events. For GSMaP SPPs, GSMaP-Gauge presented the best performance in terms of various statistical metrics, followed by GSMaP-Gauge-NRT. GSMaP-MVK and GSMaP-NRT remarkably overestimated total precipitation, and GSMaP-NOW showed an evident underestimation. By comparing the performances of IMERG and GSMaP SPPs, GSMaP-Gauge-NRT provided the best precipitation estimates among all real-time and near-real-time SPPs. For post-real-time SPPs, GSMaP-Gauge presented the highest capability at the daily scale, and IMERG-F slightly outperformed the other SPPs at the monthly scale. This study is one of the earliest studies focusing on the quality of the latest IMERG and GSMaP SPPs. The findings of this study provide SPP developers with valuable information on the quality of the latest GPM-era SPPs in YRSR and help SPP researchers to refine the precipitation retrieving algorithms to improve the applicability of SPPs. Full article

(This article belongs to the Special Issue Applications of Remote Sensing and GIS in Hydrology II)

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23 pages, 9344 KiB

Open AccessEditor’s ChoiceArticle

Extreme Floods in Small Mediterranean Catchments: Long-Term Response to Climate Variability and Change

by Gerardo Benito, Yolanda Sanchez-Moya, Alicia Medialdea, Mariano Barriendos, Mikel Calle, Mayte Rico, Alfonso Sopeña and Maria J. Machado

Water 2020, 12(4), 1008; https://doi.org/10.3390/w12041008 - 1 Apr 2020

Cited by 22 | Viewed by 5992

Abstract

Climate change implies changes in the frequency and magnitude of flood events. The influence of climate variability on flooding was evaluated by an analysis of sedimentary (palaeofloods) and documentary archives. A 500-year palaeoflood record at Montlleó River (657 km² in catchment area), [...] Read more.

Climate change implies changes in the frequency and magnitude of flood events. The influence of climate variability on flooding was evaluated by an analysis of sedimentary (palaeofloods) and documentary archives. A 500-year palaeoflood record at Montlleó River (657 km² in catchment area), eastern Spain, revealed up to 31 palaeofloods with a range of discharges of 20–950 m³ s⁻¹, and with at least five floods exceeding 740–950 m³ s⁻¹. This information contrasts with the available gauged flood registers (since year 1971) with an annual maximum daily discharge of 129 m³ s⁻¹. Our palaeoflood dataset indicates flood cluster episodes at (1) 1570–1620, (2) 1775–1795, (3) 1850–1890, and (4) 1920–1969. Flood rich periods 1 and 3 corresponded to cooler than usual (about 0.3 °C and 0.2 °C) climate oscillations, whereas 2 and 4 were characterised by higher inter-annual climatic variability (floods and droughts). This high inter-annual rainfall variability increased over the last 150 years, leading to a reduction of annual maximum flow. Flood quantiles (>50 years) calculated from palaeoflood+gauged data showed 30%–40% higher peak discharges than those using only instrumental records, whereas when increasing the catchment area (1500 km²) the discharge estimation variance decreased to ~15%. The results reflect the higher sensitivity of small catchments to changes on flood magnitude and frequency due to climate variability whereas a larger catchment buffers the response due to the limited extent of convective storms. Our findings show that extended flood records provide robust knowledge about hazardous flooding that can assist in the prioritization of low-regret actions for flood-risk adaptation to climate change. Full article

(This article belongs to the Special Issue Influence of Climate Change on Floods)

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25 pages, 6705 KiB

Open AccessEditor’s ChoiceArticle

Mapping of Groundwater Spring Potential in Karst Aquifer System Using Novel Ensemble Bivariate and Multivariate Models

by Viet-Ha Nhu, Omid Rahmati, Fatemeh Falah, Saeed Shojaei, Nadhir Al-Ansari, Himan Shahabi, Ataollah Shirzadi, Krzysztof Górski, Hoang Nguyen and Baharin Bin Ahmad

Water 2020, 12(4), 985; https://doi.org/10.3390/w12040985 - 31 Mar 2020

Cited by 62 | Viewed by 6892

Abstract

Groundwater is an important natural resource in arid and semi-arid environments, where discharge from karst springs is utilized as the principal water supply for human use. The occurrence of karst springs over large areas is often poorly documented, and interpolation strategies are often [...] Read more.

Groundwater is an important natural resource in arid and semi-arid environments, where discharge from karst springs is utilized as the principal water supply for human use. The occurrence of karst springs over large areas is often poorly documented, and interpolation strategies are often utilized to map the distribution and discharge potential of springs. This study develops a novel method to delineate karst spring zones on the basis of various hydrogeological factors. A case study of the Bojnourd Region, Iran, where spring discharge measurements are available for 359 sites, is used to demonstrate application of the new approach. Spatial mapping is achieved using ensemble modelling, which is based on certainty factors (CF) and logistic regression (LR). Maps of the CF and LR components of groundwater potential were generated individually, and then, combined to prepare an ensemble map of the study area. The accuracy (A) of the ensemble map was then assessed using area under the receiver operating characteristic curve. Results of this analysis show that LR (A = 78%) outperformed CF (A = 67%) in terms of the comparison between model predictions and known occurrences of karst springs (i.e., calibration data). However, combining the CF and LR results through ensemble modelling produced superior accuracy (A = 85%) in terms of spring potential mapping. By combining CF and LR statistical models through ensemble modelling, weaknesses in CF and LR methods are offset, and therefore, we recommend this ensemble approach for similar karst mapping projects. The methodology developed here offers an efficient method for assessing spring discharge and karst spring potentials over regional scales. Full article

(This article belongs to the Special Issue Groundwater Modelling in Karst Areas)

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17 pages, 5571 KiB

Open AccessEditor’s ChoiceArticle

Performance Investigation of the Immersed Depth Effects on a Water Wheel Using Experimental and Numerical Analyses

by Mengshang Zhao, Yuan Zheng, Chunxia Yang, Yuquan Zhang and Qinghong Tang

Water 2020, 12(4), 982; https://doi.org/10.3390/w12040982 - 30 Mar 2020

Cited by 12 | Viewed by 9122

Abstract

The purpose of this research is to study the effect of different immersed depths on water wheel performance and flow characteristics using numerical simulations. The results indicate that the simulation methods are consistent with experiments with a maximum error less than 5%. Under [...] Read more.

The purpose of this research is to study the effect of different immersed depths on water wheel performance and flow characteristics using numerical simulations. The results indicate that the simulation methods are consistent with experiments with a maximum error less than 5%. Under the same rotational speeds, the efficiency is much higher and the fluctuation amplitude of the torque is much smaller as the immersed radius ratio increases, and until an immersed radius ratio of 82.76%, the wheel shows the best performance, achieving a maximum efficiency of 18.05% at a tip-speed ratio (TSR) of 0.1984. The average difference in water level increases as the immersed radius ratio increases until 82.76%. The water area is much wider and the water volume fraction shows more intense change at the inlet stage at a deep immersed depth. At an immersed radius ratio of 82.76%, some air intrudes into the water at the inlet stage, coupled with a dramatic change in the water volume fraction that would make the flow more complex. Furthermore, eddies are found to gradually generate in a single flow channel nearly at the same time, except for an immersed depth of 1.2 m. However, eddies generate in two flow channels and can develop initial vortexes earlier than other cases because of the elevation of the upstream water level at an immersed radius ratio of 82.76%. Full article

(This article belongs to the Section Hydraulics and Hydrodynamics)

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22 pages, 2279 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Dam Break Social Impact Assessments Based on an Improved Variable Fuzzy Set Model

by Guanjie He, Junrui Chai, Yuan Qin, Zengguang Xu and Shouyi Li

Water 2020, 12(4), 970; https://doi.org/10.3390/w12040970 - 29 Mar 2020

Cited by 13 | Viewed by 4358

Abstract

In recent years attention has shifted from “dam safety” to “dam risk” due to the high loss characteristics of dam breaks. Despite this, there has been little research on social impact assessments. Variable fuzzy sets (VFSs) are a theoretical system for dealing with [...] Read more.

In recent years attention has shifted from “dam safety” to “dam risk” due to the high loss characteristics of dam breaks. Despite this, there has been little research on social impact assessments. Variable fuzzy sets (VFSs) are a theoretical system for dealing with uncertainty that are used in many industries. However, the relative membership degree (RMD) calculations required for VFSs are complicated and data can be overlooked. Furthermore, the RMD is highly subjective when dealing with qualitative problems, which can seriously affect the accuracy of the results. This study introduces grey system theory (GST) which analyzes the RMD characteristics to improve traditional VFSs. A new method for calculating the social impact of a dam break is proposed based on the correlation between the core parameters of the two theories. The Liujiatai Reservoir is used as a test case and the new and traditional evaluation methods are compared. The results show that the proposed method has advantages when dealing with uncertainty that are consistent with the characteristics of the problems associated with dam break social impact assessments. Moreover, the evaluation results obtained using the proposed method are consistent with, or more accurate than, those obtained using the traditional method. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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58 pages, 1781 KiB

Open AccessEditor’s ChoiceReview

Worldwide Regulations and Guidelines for Agricultural Water Reuse: A Critical Review

by Farshid Shoushtarian and Masoud Negahban-Azar

Water 2020, 12(4), 971; https://doi.org/10.3390/w12040971 - 29 Mar 2020

Cited by 176 | Viewed by 24073

Abstract

Water reuse is gaining momentum as a beneficial practice to address the water crisis, especially in the agricultural sector as the largest water consumer worldwide. With recent advancements in wastewater treatment technologies, it is possible to produce almost any water quality. However, the [...] Read more.

Water reuse is gaining momentum as a beneficial practice to address the water crisis, especially in the agricultural sector as the largest water consumer worldwide. With recent advancements in wastewater treatment technologies, it is possible to produce almost any water quality. However, the main human and environmental concerns are still to determine what constituents must be removed and to what extent. The main objectives of this study were to compile, evaluate, and compare the current agricultural water reuse regulations and guidelines worldwide, and identify the gaps. In total, 70 regulations and guidelines, including Environmental Protection Agency (EPA), International Organization for Standardization (ISO), Food and Agriculture Organization of the United Nations (FAO), World Health Organization (WHO), the United States (state by state), European Commission, Canada (all provinces), Australia, Mexico, Iran, Egypt, Tunisia, Jordan, Palestine, Oman, China, Kuwait, Israel, Saudi Arabia, France, Cyprus, Spain, Greece, Portugal, and Italy were investigated in this study. These regulations and guidelines were examined to compile a comprehensive database, including all of the water quality monitoring parameters, and necessary treatment processes. In summary, results showed that the regulations and guidelines are mainly human-health centered, insufficient regarding some of the potentially dangerous pollutants such as emerging constituents, and with large discrepancies when compared with each other. In addition, some of the important water quality parameters such as some of the pathogens, heavy metals, and salinity are only included in a small group of regulations and guidelines investigated in this study. Finally, specific treatment processes have been only mentioned in some of the regulations and guidelines, and with high levels of discrepancy. Full article

(This article belongs to the Section Wastewater Treatment and Reuse)

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19 pages, 2562 KiB

Open AccessEditor’s ChoiceArticle

Hydropower Generation Through Pump as Turbine: Experimental Study and Potential Application to Small-Scale WDN

by Matteo Postacchini, Giovanna Darvini, Fiorenza Finizio, Leonardo Pelagalli, Luciano Soldini and Elisa Di Giuseppe

Water 2020, 12(4), 958; https://doi.org/10.3390/w12040958 - 28 Mar 2020

Cited by 27 | Viewed by 20233

Abstract

Pump-As-Turbine (PAT) technology is a smart solution to produce energy in a sustainable way at small scale, e.g., through its exploitation in classical Water Distribution Networks (WDNs). PAT application may actually represent a suitable solution to obtain both pressure regulation and electrical energy [...] Read more.

Pump-As-Turbine (PAT) technology is a smart solution to produce energy in a sustainable way at small scale, e.g., through its exploitation in classical Water Distribution Networks (WDNs). PAT application may actually represent a suitable solution to obtain both pressure regulation and electrical energy production. This technology enables one to significantly reduce both design and maintenance costs if compared to traditional turbine applications. In this work, the potential hydropower generation was evaluated through laboratory tests focused on the characterization of a pump working in reverse mode, i.e., as a PAT. Both hydrodynamic (pressure and discharge) and mechanical (rotational speed and torque) conditions were varied during the tests, with the aim to identify the most efficient PAT configurations and provide useful hints for possible real-world applications. The experimental findings confirm the good performances of the PAT system, especially when rotational speed and water demand are, respectively, larger than 850 rpm and 8 L/s, thus leading to efficiencies greater than 50%. Such findings were applied to a small municipality, where daily distribution of pressure and discharge were recorded upstream of the local WDN, where a Pressure Reducing Valve (PRV) is installed. Under the hypothesis of PRV replacement with the tested PAT, three different scenarios were studied, based on the mean recorded water demand and each characterized by specific values of PAT rotational speed. The best performances were observed for the largest tested speeds (1050 and 1250 rpm), which lead to pressure drops smaller than those actually due to the PRV, thus guaranteeing the minimum pressure for users, but also to mechanical powers smaller than 100 W. When a larger mean water demand is assumed, much better performances are reached, especially for large speeds (1250 rpm) that lead to mechanical powers larger than 1 kW combined to head drops a bit larger than those observed using the PRV. A suitable design is thus fundamental for the real-world PAT application. Full article

(This article belongs to the Special Issue Application of Innovative Technologies for Active Control and Energy Efficiency in Water Supply Systems)

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22 pages, 6845 KiB

Open AccessEditor’s ChoiceArticle

Hydrochemical Characteristics and Water Quality Evaluation of Rivers in Different Regions of Cities: A Case Study of Suzhou City in Northern Anhui Province, China

by Yaqi Jiang, Herong Gui, Hao Yu, Meichen Wang, Hongxia Fang, Chunlei Wang, Chen Chen, Yaru Zhang and Yiheng Huang

Water 2020, 12(4), 950; https://doi.org/10.3390/w12040950 - 27 Mar 2020

Cited by 44 | Viewed by 5315

Abstract

To study the disparity of river hydrochemical characteristics and water quality in different regions of the city, this paper took the Tuo River in the center of Suzhou, Northern Anhui, China and the Bian River on the edge of the urban area as [...] Read more.

To study the disparity of river hydrochemical characteristics and water quality in different regions of the city, this paper took the Tuo River in the center of Suzhou, Northern Anhui, China and the Bian River on the edge of the urban area as the research objects, used Piper trigram, Gibbs diagram, and hydrogen and oxygen isotope content characteristics to analyze the geochemical characteristics of surface water in the study area, and then the improved fuzzy comprehensive evaluation method was used to evaluate the water quality. The results showed that the hydrochemical types of the two rivers were SO₄-Cl-Na type, and the contents of Na⁺, K⁺, SO₄²⁻, Cl⁻, Ca²⁺, total phosphorus (TP) in the Bian River at the edge of the city were much higher than those in the Tuo River at the center of the city (ANOVA, p < 0.001). Gibbs diagram showed that the ion composition of the two rivers was mainly affected by rock weathering. The results of correlation analysis and water quality evaluation showed that Bian River was greatly affected by agricultural non-point source pollution, and its water quality was poor, class IV and class V water account for 95%, while, for Tuo River, due to the strong artificial protection, class II and class III accounted for 40.74% and 59.26%, respectively, and the overall water quality was better than that of Bian River. The evaluation results of irrigation water quality showed that the samples from Tuo River were high in salt and low in alkali, which could be used for irrigation when the soil leaching conditions were good, while Bian River water samples were high in salt and medium in alkali, which was suitable for irrigation of plants with strong salt tolerance. Full article

(This article belongs to the Section Water Use and Scarcity)

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26 pages, 4432 KiB

Open AccessEditor’s ChoiceArticle

High-Resolution Mapping of Japanese Microplastic and Macroplastic Emissions from the Land into the Sea

by Yasuo Nihei, Takushi Yoshida, Tomoya Kataoka and Riku Ogata

Water 2020, 12(4), 951; https://doi.org/10.3390/w12040951 - 27 Mar 2020

Cited by 58 | Viewed by 15432

Abstract

Plastic debris presents a serious hazard to marine ecosystems worldwide. In this study, we developed a method to evaluate high-resolution maps of plastic emissions from the land into the sea offshore of Japan without using mismanaged plastic waste. Plastics were divided into microplastics [...] Read more.

Plastic debris presents a serious hazard to marine ecosystems worldwide. In this study, we developed a method to evaluate high-resolution maps of plastic emissions from the land into the sea offshore of Japan without using mismanaged plastic waste. Plastics were divided into microplastics (MicPs) and macroplastics (MacPs), and correlations between the observed MicP concentrations in rivers and basin characteristics, such as the urban area ratio and population density, were used to evaluate nationwide MicP concentration maps. A simple water balance analysis was used to calculate the annual outflow for each 1 km mesh to obtain the final MicP emissions, and the MacP input was evaluated based on the MicP emissions and the ratio of MacP/MicP obtained according to previous studies. Concentration data revealed that the MicP concentrations and basin characteristics were significantly and positively correlated. Water balance analyses demonstrated that our methods performed well for evaluating the annual flow rate, while reducing the computational load. The total plastic input (MicP + MacP) was widely distributed from 210–4776 t/yr and a map showed that plastic emissions were high for densely populated and highly urbanized areas in the Tokyo metropolitan area, as well as other large urban areas, especially Nagoya and Osaka. These results provide important insights that may be used to develop countermeasures against plastic pollution and the methods employed herein can also be used to evaluate plastic emissions in other regions. Full article

(This article belongs to the Section Water Quality and Contamination)

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19 pages, 6896 KiB

Open AccessEditor’s ChoiceArticle

A Three-Dimensional Numerical Study of Wave Induced Currents in the Cetraro Harbour Coastal Area (Italy)

by Giovanni Cannata, Federica Palleschi, Benedetta Iele and Francesco Cioffi

Water 2020, 12(4), 935; https://doi.org/10.3390/w12040935 - 26 Mar 2020

Cited by 4 | Viewed by 3148

Abstract

In this paper we propose a three-dimensional numerical study of the coastal currents produced by the wave motion in the area opposite the Cetraro harbour (Italy), during the most significant wave event for the coastal sediment transport. The aim of the present study [...] Read more.

In this paper we propose a three-dimensional numerical study of the coastal currents produced by the wave motion in the area opposite the Cetraro harbour (Italy), during the most significant wave event for the coastal sediment transport. The aim of the present study is the characterization of the current patterns responsible for the siltation that affects the harbour entrance area and the assessment of a project solution designed to limit this phenomenon. The numerical simulations are carried out by a three-dimensional non-hydrostatic model that is based on the Navier–Stokes equations expressed in integral and contravariant form on a time-dependent curvilinear coordinate system, in which the vertical coordinate moves in order to follow the free surface variations. The numerical simulations are carried out in two different geometric configurations: a present configuration, that reproduces the geometry of the coastal defence structures currently present in the harbour area and a project configuration, which reproduces the presence of a breakwater designed to modify the coastal currents in the area opposite the harbour entrance. Full article

(This article belongs to the Special Issue Numerical Modelling of Wave Fields and Currents in Coastal Area)

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18 pages, 5124 KiB

Open AccessEditor’s ChoiceArticle

Study on the Single-Multi-Objective Optimal Dispatch in the Middle and Lower Reaches of Yellow River for River Ecological Health

by Tao Bai, Xia Liu, Yan-ping HA, Jian-xia Chang, Lian-zhou Wu, Jian Wei and Jin Liu

Water 2020, 12(3), 915; https://doi.org/10.3390/w12030915 - 24 Mar 2020

Cited by 10 | Viewed by 3982

Abstract

Given the increasingly worsening ecology issues in the lower Yellow River, the Xiaolangdi reservoir is chosen as the regulation and control target, and the single and multi-objective operation by ecology and power generation in the lower Yellow River is studied in this paper. [...] Read more.

Given the increasingly worsening ecology issues in the lower Yellow River, the Xiaolangdi reservoir is chosen as the regulation and control target, and the single and multi-objective operation by ecology and power generation in the lower Yellow River is studied in this paper. This paper first proposes the following three indicators: the ecological elasticity coefficient (f1), the power generation elasticity coefficient (f2), and the ecological power generation profit and loss ratio (k). This paper then conducts a multi-target single dispatching study on ecology and power generation in the lower Yellow River. A genetic algorithm (GA) and an improved non-dominated genetic algorithm (NSGA-II) combining constraint processing and feasible space search techniques were used to solve the single-objective model with the largest power generation and the multi-objective optimal scheduling model considering both ecology and power generation. The calculation results show that: (1) the effectiveness of the NSGA-Ⅱcombined with constraint processing and feasible spatial search technology in reservoir dispatching is verified by an example; (2) compared with the operation model of maximizing power generation, the power generation of the target model was reduced by 0.87%, the ecological guarantee rate was increased by 18.75%, and the degree of the impact of ecological targets on the operating results was quantified; (3) in each typical year, the solution spatial distribution and dimensions of the single-target and multi-target models of change are represented by the Pareto-front curve, and a multi-objective operation plan is generated for decision makers to choose; (4) the f1, f2, and k indicators are selected to analyze the sensitivity of the five multi-objective plans and to quantify the interaction between ecological targets and power generation targets. Ultimately, this paper discusses the conversion relationship and finally recommends the best equilibrium solution in the multi-objective global equilibrium solution set. The results provide a decision-making basis for the multi-objective dispatching of the Xiaolangdi reservoir and have important practical significance for further improving the ecological health of the lower Yellow River. Full article

(This article belongs to the Special Issue Advances in Hydrologic Forecasts and Water Resources Management )

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24 pages, 7285 KiB

Open AccessEditor’s ChoiceArticle

Automatic Extraction of Supraglacial Lakes in Southwest Greenland during the 2014–2018 Melt Seasons Based on Convolutional Neural Network

by Jiawei Yuan, Zhaohui Chi, Xiao Cheng, Tao Zhang, Tian Li and Zhuoqi Chen

Water 2020, 12(3), 891; https://doi.org/10.3390/w12030891 - 22 Mar 2020

Cited by 15 | Viewed by 5105

Abstract

The mass loss of the Greenland Ice Sheet (GrIS) has implications for global sea level rise, and surface meltwater is an important factor that affects the mass balance. Supraglacial lakes (SGLs), which are representative and identifiable hydrologic features of surface meltwater on GrIS, [...] Read more.

The mass loss of the Greenland Ice Sheet (GrIS) has implications for global sea level rise, and surface meltwater is an important factor that affects the mass balance. Supraglacial lakes (SGLs), which are representative and identifiable hydrologic features of surface meltwater on GrIS, are a means of assessing surface ablation temporally and spatially. In this study, we have developed a robust method to automatically extract SGLs by testing the widely distributed SGLs area—in southwest Greenland (68°00′ N–70°00′ N, 48°00′ W–51°30′ W), and documented their dynamics from 2014 to 2018 using Landsat 8 OLI images. This method identifies water using Convolutional Neural Networks (CNN) and then extracts SGLs with morphological and geometrical algorithms. CNN combines spectral and spatial features and shows better water identification results than the widely used adaptive thresholding method (Otsu), and two machine learning methods (Random Forests (RF) and Support Vector Machine (SVM)). Our results show that the total SGLs area varied between 158 and 393 km² during 2014 to 2018; the area increased from 2014 to 2015, then decreased and reached the lowest point (158.73 km²) in 2018, when the most limited surface melting was observed. SGLs were most active during the melt season in 2015 with a quantity of 700 and a total area of 393.36 km². The largest individual lake developed in 2016, with an area of 9.30 km². As for the elevation, SGLs were most active in the area, with the elevation ranging from 1000 to 1500 m above sea level, and SGLs in 2016 were distributed at higher elevations than in other years. Our work proposes a method to extract SGLs accurately and efficiently. More importantly, this study is expected to provide data support to other studies monitoring the surface hydrological system and mass balance of the GrIS. Full article

(This article belongs to the Special Issue Applications of Remote Sensing and GIS in Hydrology II)

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26 pages, 4514 KiB

Open AccessEditor’s ChoiceArticle

Sustainable Water Resources Management in an Arid Area Using a Coupled Optimization-Simulation Modeling

by Siamak Farrokhzadeh, Seyed Arman Hashemi Monfared, Gholamreza Azizyan, Ali Sardar Shahraki, Maurits W. Ertsen and Edo Abraham

Water 2020, 12(3), 885; https://doi.org/10.3390/w12030885 - 21 Mar 2020

Cited by 35 | Viewed by 6555

Abstract

Severe water scarcity in recent years has magnified the economic, social, and environmental significance of water stress globally, making optimal planning in water resources necessary for sustainable socio-economic development. One of the regions that is most affected by this is the Sistan region [...] Read more.

Severe water scarcity in recent years has magnified the economic, social, and environmental significance of water stress globally, making optimal planning in water resources necessary for sustainable socio-economic development. One of the regions that is most affected by this is the Sistan region and its Hamoun wetland, located in south-east Iran. Water policies are essential to sustain current basin ecosystem services, maintaining a balance between conflicting demands from agriculture and the protection of wetland ecosystems. In the present study, a multi-objective optimization model is linked with the Water Evaluation and Planning (WEAP) software to optimize water allocation decisions over multiple years. We formulate and parameterize a multi-objective optimization problem where the net economic benefit from agriculture and the supply of environmental requirements were maximized, to analyze the trade-off between different stakeholders. This problem is modeled and solved for the study area with detailed agricultural, socio-economic, and environmental data for 30 years and quantification of ecosystem services. By plotting Pareto sets, we investigate the trade-offs between the two conflicting objectives and evaluate a possible compromise. The results are analyzed by comparing purely economic versus multi-objective scenarios on the Pareto front. Finally, the disadvantages and advantages of these scenarios are also qualitatively described to help the decision process for water resources managers. Full article

(This article belongs to the Special Issue Integrated Assessment of the Water–Energy–Land Nexus)

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21 pages, 4364 KiB

Open AccessEditor’s ChoiceArticle

Estimating 500-m Resolution Soil Moisture Using Sentinel-1 and Optical Data Synergy

by Myriam Foucras, Mehrez Zribi, Clément Albergel, Nicolas Baghdadi, Jean-Christophe Calvet and Thierry Pellarin

Water 2020, 12(3), 866; https://doi.org/10.3390/w12030866 - 20 Mar 2020

Cited by 36 | Viewed by 7545

Abstract

The aim of this study is to estimate surface soil moisture at a spatial resolution of 500 m and a temporal resolution of at least 6 days, by combining remote sensing data from Sentinel-1 and optical data from Sentinel-2 and MODIS (Moderate-Resolution Imaging [...] Read more.

The aim of this study is to estimate surface soil moisture at a spatial resolution of 500 m and a temporal resolution of at least 6 days, by combining remote sensing data from Sentinel-1 and optical data from Sentinel-2 and MODIS (Moderate-Resolution Imaging Spectroradiometer). The proposed methodology is based on the change detection technique, applied to a series of measurements over a three-year period (2015 to 2018). The algorithm described here as “Soil Moisture Estimations from the Synergy of Sentinel-1 and optical sensors (SMES)” proposes different options, allowing information from vegetation densities and seasonal conditions to be taken into account. The output from this algorithm is a moisture index ranging between 0 and 1, with 0 corresponding to the driest soils and 1 to the wettest soils. This methodology has been tested at different test sites (South of France, Central Tunisia, Western Benin and Southwestern Niger), characterized by a wide range of different climatic conditions. The resulting surface soil moisture estimations are compared with in situ measurements and already existing satellite-derived soil moisture ASCAT (Advanced SCATterometer) products. They are found to be well correlated, for the African regions in particular (RMSE below 6 vol.%). This outcome indicates that the proposed algorithm can be used with confidence to estimate the surface soil moisture of a wide range of climatically different sites. Full article

(This article belongs to the Special Issue Applications of Remote Sensing and GIS in Hydrology II)

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17 pages, 252 KiB

Open AccessEditor’s ChoiceArticle

Drought Victims Demand Justice: Politicization of Drought by Farmers in Southern Germany over Time

by Wibke Müller

Water 2020, 12(3), 871; https://doi.org/10.3390/w12030871 - 20 Mar 2020

Cited by 5 | Viewed by 3976

Abstract

Farmers have an important role in problematizing and politicizing drought. Following the argumentative turn in policy analysis, the paper analyzes the process of problem definition by means of a framing analysis, zooming in on four major drought events covered in German farming sector [...] Read more.

Farmers have an important role in problematizing and politicizing drought. Following the argumentative turn in policy analysis, the paper analyzes the process of problem definition by means of a framing analysis, zooming in on four major drought events covered in German farming sector journals that are published by farmers’ associations. The article compares the framing of the four most-cited drought events—1947, 1975–76, 2003, and 2011–12—in order to better understand how problematization has changed over time, and how farmers justify and rationalize calls for political action. Three research questions are answered: What problems are named by farmers journals when describing drought events, and what solutions are proposed? Who is considered responsible for problems and solutions? How has framing of drought changed over time? The paper shows that farmers frame drought as a matter of justice and assert their perceived right to subsidies, compensation, farmer-friendly tax policies, and market regulations by the state. From 2003, drought has been framed in association with climate change. The data findings suggest that there is no post-productivist, post-exceptionalist paradigm shift connected to proposed drought policy solutions. Drought framings appear to be persistent, giving priority to assured farmers’ incomes, not water distribution. Considering the lobby power of farmers’ associations in Germany, this finding helps to understand why state interventions remain the same over time. Full article

(This article belongs to the Special Issue Attention and Water Governance: An Agenda-Setting Perspective)

24 pages, 6850 KiB

Open AccessEditor’s ChoiceArticle

Classification of Management Alternatives to Combat Reservoir Sedimentation

by Gregory L. Morris

Water 2020, 12(3), 861; https://doi.org/10.3390/w12030861 - 19 Mar 2020

Cited by 89 | Viewed by 16854

Abstract

Sedimentation is steadily depleting reservoir capacity worldwide, threatening the reliability of water supplies, flood control, hydropower energy and other benefits that form the basis of today’s water-intensive society. The strategies available to combat reservoir sedimentation may be classed into four broad categories. Three [...] Read more.

Sedimentation is steadily depleting reservoir capacity worldwide, threatening the reliability of water supplies, flood control, hydropower energy and other benefits that form the basis of today’s water-intensive society. The strategies available to combat reservoir sedimentation may be classed into four broad categories. Three proactive categories seek to improve the sediment balance across reservoirs by: (a) reducing sediment yield from the watershed, (b) routing sediment-laden flows around or through the storage pool, and (c) removing deposited sediment following deposition. The fourth category (d) consists of strategies that adapt to capacity loss, without addressing the sediment balance. Successful management will typically combine multiple strategies. This paper presents a comprehensive classification of both proactive and adaptive strategies, consistent with current international practice. Functional descriptions and examples are given for each strategy, and criteria are provided to differentiate between them when there is potential for ambiguity. The classification categories can be used as a checklist of strategies to consider in evaluating sediment management alternatives for new designs as well as remedial work at existing sediment-challenged reservoirs. This will also help practitioners to more clearly describe and communicate the nature of their management activities. Widespread application of both active and adaptive strategies is required to bring sedimentation under control to sustain benefits of water storage for today’s and future generations. Full article

(This article belongs to the Special Issue Reservoir Sustainability: Engineering, Economics, and Ecosystems)

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31 pages, 5735 KiB

Open AccessEditor’s ChoiceReview

CFD Modeling of Effluent Discharges: A Review of Past Numerical Studies

by Abdolmajid Mohammadian, Hossein Kheirkhah Gildeh and Ioan Nistor

Water 2020, 12(3), 856; https://doi.org/10.3390/w12030856 - 18 Mar 2020

Cited by 27 | Viewed by 5785

Abstract

Effluent discharge mixing and dispersion have been studied for many decades. Studies began with experimental investigations of geometrical and concentration characteristics of the jets in the near-field zone. More robust experiments were performed using Laser-Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV) systems [...] Read more.

Effluent discharge mixing and dispersion have been studied for many decades. Studies began with experimental investigations of geometrical and concentration characteristics of the jets in the near-field zone. More robust experiments were performed using Laser-Induced Fluorescence (LIF) and Particle Image Velocimetry (PIV) systems starting in the 20th century, which led to more accurate measurement and analysis of jet behavior. The advancement of computing systems over the past two decades has led to the development of various numerical methods, which have been implemented in Computational Fluid Dynamics (CFD) codes to predict fluid motion and characteristics. Numerical modeling of mixing and dispersion is increasingly preferred over laboratory experiments of effluent discharges in both academia and industry. More computational resources and efficient numerical schemes have helped increase the popularity of using CFD models in jet and plume modeling. Numerous models have been developed over time, each with different capabilities to facilitate the investigation of all aspects of effluent discharges. Among these, Reynolds-averaged Navier-Stokes (RANS) and Large Eddy Simulations (LES) are at present the most popular CFD models employing effluent discharge modeling. This paper reviews state-of-the-art numerical modeling studies for different types and configurations of discharges, including positively and negatively buoyant discharges, which have mostly been completed over the past two decades. The numerical results of these studies are summarized and critically discussed in this review. Various aspects related to the impact of turbulence models, such as k-ε and Launder-Reece-Rodi (LRR) models, are reviewed herein. RANS and LES models are reviewed, and implications for the simulation of jet and plume mixing are discussed to develop a reference for future researchers performing numerical investigations on jet mixing and dispersion. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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14 pages, 2647 KiB

Open AccessEditor’s ChoiceArticle

Nonlinear Autoregressive Neural Networks to Predict Hydraulic Fracturing Fluid Leakage into Shallow Groundwater

by Reza Taherdangkoo, Alexandru Tatomir, Mohammad Taherdangkoo, Pengxiang Qiu and Martin Sauter

Water 2020, 12(3), 841; https://doi.org/10.3390/w12030841 - 17 Mar 2020

Cited by 39 | Viewed by 4667

Abstract

Hydraulic fracturing of horizontal wells is an essential technology for the exploitation of unconventional resources, but led to environmental concerns. Fracturing fluid upward migration from deep gas reservoirs along abandoned wells may pose contamination threats to shallow groundwater. This study describes the novel [...] Read more.

Hydraulic fracturing of horizontal wells is an essential technology for the exploitation of unconventional resources, but led to environmental concerns. Fracturing fluid upward migration from deep gas reservoirs along abandoned wells may pose contamination threats to shallow groundwater. This study describes the novel application of a nonlinear autoregressive (NAR) neural network to estimate fracturing fluid flow rate to shallow aquifers in the presence of an abandoned well. The NAR network is trained using the Levenberg–Marquardt (LM) and Bayesian Regularization (BR) algorithms and the results were compared to identify the optimal network architecture. For NAR-LM model, the coefficient of determination (R²) between measured and predicted values is 0.923 and the mean squared error (MSE) is 4.2 × 10⁻⁴, and the values of R² = 0.944 and MSE = 2.4 × 10⁻⁴ were obtained for the NAR-BR model. The results indicate the robustness and compatibility of NAR-LM and NAR-BR models in predicting fracturing fluid flow rate to shallow aquifers. This study shows that NAR neural networks can be useful and hold considerable potential for assessing the groundwater impacts of unconventional gas development. Full article

(This article belongs to the Special Issue Contaminant Transport and Fate)

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22 pages, 2867 KiB

Open AccessEditor’s ChoiceArticle

Copula-Based Multivariate Frequency Analysis of the 2012–2018 Drought in Northeast Brazil

by João Dehon Pontes Filho, Francisco de Assis Souza Filho, Eduardo Sávio Passos Rodrigues Martins and Ticiana Marinho de Carvalho Studart

Water 2020, 12(3), 834; https://doi.org/10.3390/w12030834 - 16 Mar 2020

Cited by 66 | Viewed by 5854

Abstract

The 2012–2018 drought was such an extreme event in the drought-prone area of Northeast Brazil that it triggered a discussion about proactive drought management. This paper aims at understanding the causes and consequences of this event and analyzes its frequency. A consecutive sequence [...] Read more.

The 2012–2018 drought was such an extreme event in the drought-prone area of Northeast Brazil that it triggered a discussion about proactive drought management. This paper aims at understanding the causes and consequences of this event and analyzes its frequency. A consecutive sequence of sea surface temperature anomalies in the Pacific and Atlantic Oceans, at both the decadal and interannual scales, led to this severe and persistent drought. Drought duration and severity were analyzed using run theory at the hydrographic region scale as decision-makers understand impact analysis better at this scale. Copula functions were used to properly model drought joint characteristics as they presented different marginal distributions and an asymmetric behavior. The 2012–2018 drought in Ceará State had the highest mean bivariate return period ever recorded, estimated at 240 years. Considering drought duration and severity simultaneously at the level of the hydrographic regions improves risk assessment. This result advances our understanding of exceptional events. In this sense, the present work proposes the use of this analysis as a tool for proactive drought planning. Full article

(This article belongs to the Special Issue Management of Hydrological Extremes: Floods and Droughts)

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27 pages, 4066 KiB

Open AccessEditor’s ChoiceArticle

Unsustainability Syndrome—From Meteorological to Agricultural Drought in Arid and Semi-Arid Regions

by Ali Torabi Haghighi, Nizar Abou Zaki, Pekka M. Rossi, Roohollah Noori, Ali Akbar Hekmatzadeh, Hossein Saremi and Bjørn Kløve

Water 2020, 12(3), 838; https://doi.org/10.3390/w12030838 - 16 Mar 2020

Cited by 62 | Viewed by 5967

Abstract

Water is the most important resource for sustainable agriculture in arid and semi-arid regions, where agriculture is the mainstay for rural societies. By relating the water usage to renewable water resources, we define three stages from sustainable to unsustainable water resources: (1) sustainable, [...] Read more.

Water is the most important resource for sustainable agriculture in arid and semi-arid regions, where agriculture is the mainstay for rural societies. By relating the water usage to renewable water resources, we define three stages from sustainable to unsustainable water resources: (1) sustainable, where water use is matched by renewable water capacity, ensuring sustainable water resources; (2) transitional, where water use occasionally exceeds renewable water capacity; and (3) unsustainable, with lack of water resources for agriculture, society, and the environment. Using available drought indicators (standardized precipitation index (SPI) and streamflow drought index (SDI)) and two new indices for agricultural drought (overall agricultural drought index (OADI) and agricultural drought index (ADI)), we evaluated these stages using the example of Fars province in southern Iran in the period 1977–2016. A hyper-arid climate prevailed for an average of 32% of the province’s spatio-temporal coverage during the study period. The area increased significantly from 30.6% in the first decade (1977–1986) to 44.4% in the last (2006–2015). The spatiotemporal distribution of meteorological drought showed no significant negative trends in annual precipitation during 1977–2016, but the occurrence of hydrological droughts increased significantly in the period 1997–2016. The expansion of irrigated area, with more than 60% of rainfed agriculture replaced by irrigated agriculture (especially between 1997 and 2006), exerted substantial pressure on surface water and groundwater resources. Together, climate change, reduced river flow, and significant declines in groundwater level in major aquifers led to unsustainable use of water resources, a considerable reduction in irrigated area, and unsustainability in agricultural production in the period 2006–2015. Analysis of causes and effects of meteorological, hydrological, and agricultural drought in the area identified three clear stages: before 1997 being sustainable, 1997–2006 being transitional, and after 2006 being unsustainable. Full article

(This article belongs to the Section Water Resources Management, Policy and Governance)

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